1. Field of the Invention
The present invention relates to a semiconductor device comprising an excess resin portion, a manufacturing method thereof and an apparatus for manufacturing the semiconductor device comprising a excess resin portion.
2. Description of Related Art
A manufacturing method of a semiconductor device, generally includes: a step of preparing a lead frame having a plurality of leads and a plurality of dam bars for connecting the plurality of leads; a step of mounting a semiconductor chip on the lead frame; a step of encapsulating the semiconductor chip in a resin body; and a step of cutting and removing the dam bars and separate into individual semiconductor devices. FIG. 1 illustrates a schematic plan view of a partly finished product of a semiconductor device where a plurality of semiconductor devices is manufactured on the lead frame 2. FIG. 2 illustrates an enlarged schematic view of one semiconductor device illustrated in FIG. 1. The lead frame 2 includes a plurality of leads 2b (bar line portions) extending in the lateral direction on the drawing from a resin body 3, and a plurality of dam bars 2a (hatched line portions) each connecting between two adjacent leads 2b. In a step of encapsulating a semiconductor chip (not illustrated in the figure), usually, an excess resin portion 4 is formed in a region surrounded by the resin body 3, two adjacent leads 2b and the dam bar 2a connecting between the two adjacent leads 2b. Usually, the excess resin portions 4 have a thickness equivalent to that of the lead frame 2. Since the excess resin portions 4 are formed simultaneously with the resin body 3 at the time of resin encapsulating.
The cut mode of the dam bars of a related art will be described. FIG. 3 illustrates a schematic plan view at a time when the dam bars 2a are cut by using punches 15. The dam bars 2a are cut by using the punches 15 and a cutting die which is not illustrated in the figure. In FIG. 3, each of the punch 15 is illustrated as a planar projected form of each of the cutting edge thereof, and it has a rectangular shape. Portions thereof except for the cutting edge (for example, a portion of a blade of the punch, or the like) are not illustrated. When cutting the dam bars 2a, in order to cut them reliably, a part of the punches 15 are caused to overlap even with the excess resin portions 4 in consideration of a positional shift between the dam bars 2a and the punches 15. For this reason, at the same time when the dam bars 2a are cut, a part of the excess resin portions 4 will be also punched through.
FIG. 4 illustrates a partial schematic view of a semiconductor device 11 after the plurality of dam bars are cut by using the punches 15 illustrated in FIG. 3. The part of the excess resin portions 4 overlapping with the punches 15 are punched through, leaving a plurality of excess resin portions 14 are remained. On each of the outer edge of the remaining excess resin portions 14, a cut line 14a is formed between each left lead 2b and each right lead 2b. 
In addition, as the gap increases between the dam bar 2a and the resin body 3, the area of the remaining excess resin portion 14 becomes large so that the remaining excess resin portion 14 might inconveniently drop off, which may require a step of removing the remaining excess resin portion 14 besides the step of cutting the dam bar 2a. 
In the manufacturing methods of a semiconductor device described in Japanese Patent Laid-Open Nos. 63-73656 and 07-297339, a lead frame outward of the resin body is provided with openings having a width wider than the cut width of the dam bar only at portions close to the resin body. Moreover, as another means, by reducing the gap between the dam bar and the resin body (for example, equal to or smaller than 0.3 mm) so as to cause the excess resin portion to be small, the step of removing the excess resin portion is eliminated. Moreover, in a dam bar cutting mold described in Japanese Patent Laid-Open No. 11-347645, the punch portion overlapping with the excess resin portion part has a trapezoidal shape which converges from the base portion (dam bar side) to the tip end portion (resin body side) to prevent the excess resin portion from dangling when the dam bar is cut.
We have now recognized that, according to the above-mentioned prior art, the semiconductor chip inside the resin body 3 and the resin body 3 will suffer from defects such as cracks. When the dam bars 2a are cut using rectangular punches 15 as illustrated in FIG. 3, or punches each having a trapezoid cut plane as described in Japanese Patent Laid-Open No. 11-347645, the excess resin portions 4 will be punched through at the vicinity of the resin body 3. Since the shape of the punches 15 in FIG. 3 has large overlapping area between the excess resin portions 4 and the punches 15, strong stress will be imparted to the resin body 3 through the excess resin portions 4. Because, due to a low rigidity of the excess resin portion 4, tearing stress will be generated when the excess resin portions 4 are cut by the punches 15. Therefore, defects such as cracks may occur in the semiconductor chip inside the resin body 3 or the resin body 3. In particular, with the recent miniaturization and thinning of electronic equipment, the semiconductor device used in the electronic equipment is also miniaturized and thinned, and therefore defects tend to occur more easily.
Further, a large overlapping area of the excess resin portions 4 and the punches 15 increases the amount of generated debris of the excess resin portion. Therefore, in a successive operation of cutting the dam bars, a problem in dam bar cutting may occur due to the debris of the excess resin portion entering in the cutting die.